How to restore a weakened shaft for a bearing

A jammed bearing can rotate on the shaft, gradually erasing it by fractions of millimeters. If you do not change it immediately, then in the future the new bearing will no longer fit, so you will need to build up the leaky shaft. This is usually done by electric welding and then the part is processed on a lathe. In cases where this method is unacceptable, you can use the method of electric spark microwelding.

Materials and tools:

• sandpaper;
  
• piece of electrode d3 mm without coating;
  
• drill;
  
• power supply 10-15V, 5-10A;
  
• clamp for cylindrical connections.

A transformer, a car battery charger or a welding inverter at minimum settings can be used as a power source. The use of the latter is less desirable, since often its power will be too much even at the weakest settings.

Shaft deposition

After dismantling the bearing, it is necessary to grind the shaft at the extension site.

Next, the diameter is measured to determine the required height of metal welding.

A small piece of welding electrode.

We remove the coating, straighten and polish to a shine.

Clamp it in the chuck of an electric drill or screwdriver.

A wire from the power source is connected to it on the side. Polarity doesn't matter. It can be secured with an alligator clip or simply wound. The second wire from the power source is fixed to the shaft. It should be fixed in an insignificant place that can be slightly damaged by fusing.
Voltage is applied to the power source, after which the drill starts. A rotating electrode with a fixed wire is applied to the shaft at the point of extension. As a result, a microwelding process occurs. The metal from the electrode is directed to the shaft. This happens very slowly and in a thin layer. By moving the electrode along the shaft without gaps, approximately 0.05-0.1 mm of thickness can be applied in one layer.



After welding, each layer must be sanded with sandpaper to remove slag. Layers are applied repeatedly until the shaft reaches the required thickness. Thus, even with minor wear of 1 mm, at least 10 layers will have to be applied.


Having restored the required thickness and re-sanded the shaft with sandpaper, a cylindrical joint retainer is applied.


The bearing is mounted on top.


The liquid fixative will fill all the pores in the welded metal and the gap between the shaft and the bearing. Once cured, it will provide very good additional hold. Thanks to this, the new bearing race will no longer rotate, but will become smooth without play.

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